MODifying theIsland map(removing and adding resource nodes)

i have made some new ores (copper, iron, and gold) and their respective ingots.
I have also made their own rocks(resource nodes) and ready to start placing.

I have looked at some tutorials on adding a new submap layer and placing them there.
I am stuck on wanting to remove the metal rock resource nodes(is this possible without making map from scratch?)?

I simply would like to select all metal ore resource nodes and remove then on new layer(or existing) add my ore resources.

Thanks for the help and suggestions in advance.

Just a thought… but what about simply change some of the existing resource nodes… to your new type?